They’re not when I have to specifically buy a 3.0 cable to connect my computer to my drive enclosure for it to operate as intended.
The majority of them are 2.0 cables, which is fine for users who care more about fast charging their phones, but not as data cables.
The USB-IF could have made all USB-C cables meet 3.0 at a minimum, but it didn’t. What sense did it make to create a fancy new connector to usher in the new era of fast data, and then allow cables using the same connector to be gimped to 2.0 speeds? That’s not full forward progress.
And there’s the silliness of the whole 3.x Gen1/Gen2 naming scheme, which is a separate issue, created by geeks, for geeks. The average Joe who has.a hard time telling if their phone is fast charging stands no chance trying to sort out that mess.